1. Field of the Invention
This invention relates to indication of temperatures for frozen products.
2. Description of the Prior Art
The copending application described above discloses a vessel (an indicator) having one or more cavities, each of which is partly filled with indicator fluid, that at certain temperatures freeze. During freezing, at first the indicator is placed in a first position, and under the influence of gravity, the indicator fluids flow into the deepest part of the cavities and freeze in the first part of the cavities. After freezing the indicator is brought into another, second position, i.e. is inverted, so that during any melting, the indicator fluids flow into a second part of the cavities; this second part is then the deepest part of the cavity.
This procedure and the various disclosed embodiments are for temperature control for freezing equipment.
The problem for the monitoring of cold-storage and frozen products is different, because one should assume at the beginning, that in storage and later while the products are displayed, such as in a deep-freezer, that the products are moved arbitrarily, so that under circumstances of melting of the indicator fluids one cannot necessarily observe if the indicator has been inverted to the freezing position by chance.
For these reasons, the copending patent application's described method does not suit the temperature control of movable products.